Split Phase Motor

Thanks

Split phase motors are cheapest to manufacture, but have lowest power factor and overall energy efficiency - which is not a big deal for a fractional HP motor. However split phase motors also suffer from low starting torque characteristics. Thus they are fine for easy starting applications like fans or bench grinders, but are not good for a hard-starting loads like air compressors.

Capacitor start motors have much higher starting torque characterists, but draw a lot of current at startup. Repulsion motors also have high starting torque, but they require much less peak starting current than capacitor motors. However repulsion motors are mechanically the most complex (have a commutator, starting brushes and a centrifugal brush lifting mechanism) hence are most costly to make. ...Bob M

All "split phase" motors are single phase motors, but not all single phase motors are split phase.

Single phase ac motors all need some way to start them. The most common types of ac motors are split phase and capacitor start. Split phase motors have low starting torque, so they tend to be fractional horsepower motors where small size matters more than torque. Capacitor start motors have better starting torque than split phase, so you see them in larger sizes.

Three phase motors don't need any starting circuit, which is why you will never see split phase or capacitor start three phase motors.

A split phase motor uses two stator windings, a start winding and a run winding. The motor starts on both windings and at 75% of rated rpm the start winding is droped out of the circuit either by a relay or centrifugal switch.

A 3-phase motor has 3 windings. Power is continously applied to all three windings.

Theres lots of variations of the above motors and covers a large area with too much typing for this forum. One of the best books on the subject is Moderen Refrigeration by Goodheart/Wilcox. This text explains electrical circuits in a very simple mannor but at the same time very indepth in technical therory.

T_Bone